1. Field of the Invention
This invention relates to a burning condition detecting device and burning control device in an internal combustion engine which is capable of detecting and controlling an air-fuel ratio of an air-fuel mixture gas at a lean limit and a theoretical range so as to ensure a stable running of the internal combustion engine.
2. Description of Prior Art
With the demand of purifying emition gas and enhancing fuel efficiency of internal combustion engine, it has been desired to detect burning condition in each cylinder of the internal combustion engine so as to run the engine at a lean limit of an air-fuel ratio. With the combination of a pumping element and an oxygen sensor, an air-fuel sensor is used to detect an air-fuel ratio of the air-fuel mixture gas on the basis of an oxygen component and an unconsumed fuel in the exhaust gas to carry out a lean burning in each cylinder of the internal combustion engine.
In a burning control device using the air-fuel sensor, however, the air-fuel ratio is controlled to normally burn the leanest air-fuel mixture gas by considering the concentration variation of the mixture gas depending on the cylinder of the internal combustion engine. For this reason, the air-fuel ratio of the mixture gas tends to be greater so as to invite difficulty in purifying emition gas and enhancing fuel efficiency of internal combustion engine.
The invention is made on the basis of the fact that an electrical current variation flowing between electrodes of a spark plug increases with the air-fuel mixture gas approaching to a critical air-fuel ratio which is in a lower limit the internal combustion engine can run.
Therefore, it is an object of the invention to provide a burning condition detecting device and burning control device which is capable of controlling an air-fuel mixture gas in each cylinder at a critical air-fuel ratio which is in a lower limit the internal combustion engine can run.